This invention relates to an arrangement for fixing a guide blade segment that forms part of a transition channel.
Modern aircraft gas turbines frequently comprise a so-called core engine with a high-pressure turbine having a relatively small diameter, which is arranged downstream from a low-pressure turbine having a relatively large diameter. This creates the necessity of transitioning the ring channel, which extends through the gas turbine and is equipped with guide blades, behind the high-pressure turbine from its small diameter to the large diameter of the low-pressure turbine, which occurs with the aid of a so-called transition channel.
Such engines furthermore have high bypass ratios and low speeds of the low-pressure turbine shaft, which is generally separated in relation to the high-pressure turbine shaft; moreover the urgency exists to design the core engines in an increasingly compact and powerful manner, which leads to increasingly longer axially extending transition channels with greater differences between the radii of the channel cross-sections that need to be taken into consideration.
Such an arrangement, which is called a “transition duct sealing device”, is known from German publication DE 37 00 668 A1. The inner wall (16) of the transition duct consists of several segments (18), which are screwed together with the inner shrouds (20) of the guide blade clusters (22). Additional, cone-shaped parts (34, 42) with seal elements (40, 70) are screwed to the segments (18). The screw connection between the rear cone (42) and the segments (18) permits limited relative axial and radial movements, with the cone (42) comprising slots (46), in which bolts (32) are guided with some play. Hence the guide blade clusters (22) bear the segments (18) and the cones (34, 42), and no information is provided on the fastening of the guide blade clusters (22) on the outer turbine housing.
German publication DE 24 35 071 C1 protects a stator blade for a gas turbine jet engine, i.e. a guide vane. The guide vane (20) is located on the downstream end of the combustion device (12) upstream from a turbine rotor stage (16) of the high-pressure turbine. Due to the high gas temperatures directly behind the combustion chamber, the guide vane (20) has an air-cooled design. The pressure of the cooling air is also used to stabilize and align the multi-part blade design during operation. Hence, no integral, inherently stable guide blade segments exist.
British document GB 2 260 789 A relates to an arrangement for fixing guide blade segments. The guide blade segments (10) are fastened to the turbine housing and guided only via their outer platform, i.e. their outer band (12). For this purpose each band (12) contains on the upstream end a flange (30) that is hook-shaped in its longitudinal section. The flange is supported on one side radially on a housing part (32). On the downstream end each band (12) is equipped with a support member (26), a hook (22) and a land (24). Each support member (26) engages in the circumferential direction into the recess (24) of the adjoining guide blade segment (10). Between the support member (26), recess (24), and hook (22), a small free space remains, in which a stud (28) that is attached to the housing engages in an axial fashion. The area assumes a radial fixation as well as a rotational prevention function in the circumferential direction. Furthermore, the bands here rest axially on a housing component (18). In the area of the guide elements (22, 24, 26, 28), the design is relatively complex as well problematic from a stability point of view.
This is where the invention comes in, the object of which is to create an inexpensive, easy-to-mount and well-sealing arrangement that is at the same time, weight-saving, for the attachment of a guide blade segment that forms part of a transition channel.
This object is achieved pursuant to the invention.
The design pursuant to the invention has a series of advantages. For example, a simple and safely functioning seal of the guide blade segments on the inside and outside, and thus to the disk area between the high-pressure and low-pressure turbine, is possible through the straight surface contact between the bars and bearing surfaces of the housing and the bearing pedestal. Through the groove-hook-type connection in the front area of the outer platform of the guide blade segment, these are held radially in the turbine housing in a safe and permanent fashion and are fixed in the circumferential direction by means of the pins engaging in the groove-hook-type connection. The bearing area located on the turbine housing for accommodating the guide blade segment can at the same time serve as a bearing area for a channel segment of the transition channel engaging likewise on the bearing surface so that the mounted guide blade segment of the transition channel is a locking element for the channel segment arranged upstream.
The arrangement pursuant to the invention of the grooves on the groove-hook-type connection on the housing and the arrangement of the hooks on the outside platform part of the channel segment enables a simple and accurate production of these parts, leading to significant weight and cost advantages.
The invention is described in the following based on an exemplary embodiment illustrated in the drawings in a more or less diagrammatic fashion.